11-13-2000, 09:29 AM
View Full Version : what's the difference between a centrifuge s/charger and a rootstype s/charger?
11-13-2000, 09:29 AM
11-14-2000, 10:10 AM
The centrifugal (Vortech, Novi, etc ...) have a linear boost curve therfore the more RPMs = more boost.
Roots (Eaton, etc ...) provide torque down low so their boost curve peaks early and maintains that boost throughout the RPM band.
The roots will provide more torque down low, but will not be able to achieve the same boost numbers as the centrifugals.
11-28-2000, 07:22 AM
The Rootes-type is a positive displacement design. It moves exactly the same amount of air for every revolution. Double the crank speed and it flows double the amount of air per minute. Changing pullies (hence blower speed) will increase or decrease boost.
The sealing required by the Rootes calls for tight clearances and can generate a fair amount of mechanical friction heat. An intercooler to control charge temperature can be used to offset the heat that comes from compressing the charge as well as any heat transferred from the blower itself.
The Rootes blower gives immediate power gains from idle speed on up. It makes your engine feel bigger. No sudden peak or long flat spot. Every top fuel dragster and funny car has this kind of blower sitting on top of the engine.
The centrifugal style is actually an engine-driven version of the same kind of compressor that is in a turbocharger. In other words, a turbocharger is an exhaust-driven centrifugal supercharger. The centrifugal design generates boost that rises geometrically with compressor speed. A setup that provides a big push in the mid-to-upper rev range may be uninspiring off the line. High pressure at lower speeds may prove too much at redline. A wastegate is critical!
The ideal centrifugal set up runs the compressor at a higher relative speed at low rpms and trails off the ratio as crank speed rises. This has been done by v-belt drive with split-pullies (similar to snowmobile automatic transmission).
The two halves of the pulley look like this: )( . When the two pulley faces are close together the v-belt rides around a large circumference. When the faces are further apart ) ( , the belt rides around closer to the hub. The pulley adjustment can be done by electricity, oil pressure, etc.